SOFIA, April 10 (Reuters) - Georgi Kadiev is, like many of his fellow Bulgarians, caught between Russia and the West.

A member of parliament with the ruling Socialist party, his government has gone along with sanctions on Moscow over its annexation of Crimea, but at the same time he feels the cultural and historical pull of Bulgaria's long association with Russia.

"My father was an officer in the Soviet army," he said. "He spent his life shoulder to shoulder with the Soviet army. It's very hard to explain to him now that we should impose sanctions on Russia."

Bulgaria has long been an anomaly in Europe, a country inside the European Union and the NATO military alliance, yet which feels close to Russia. That tension has been thrown into even sharper relief by the stand-off over Ukraine, with many feeling under pressure to choose between Moscow and Brussels.

Bulgaria is now facing its sternest test of loyalty to the European Union since joining in 2007 and has not wavered, even though it risks economic hardship and a domestic backlash could topple Prime Minister Plamen Oresharski's fragile coalition.

The danger for the government is that the nationalist Attack party - on whose support the Socialists rely to stay in power - could carry out a threat to withdraw their unofficial support if Sofia backs more EU sanctions against the Kremlin.

Bulgaria is highly vulnerable to the political fallout of the Crimea crisis compared to other countries formerly behind the Iron Curtain such as pro-Western Poland, or fellow 2007 EU entrant Romania, which had already begun to drift from Moscow in Communist times and is less hooked on Russian energy supplies.

Many former Communist countries in the EU kept ties to Moscow but most view Russia as a former occupier and still a threat. Bulgaria is different because it sees Moscow as a friend. When its economic and cultural ties are taken together, it is probably the EU state closest to Moscow.

But Sofia has gone along with initial EU sanctions against Moscow and its foreign minister said in an interview that it would not veto more punitive measures if they were imposed.

"We are not going to impose a veto, in the same time we are not going to push for such sanctions," Bulgarian Foreign Minister Kristian Vigenin told Reuters.

"The risks for us are high. We are one of the most vulnerable countries. We have made that clear and our partners know that very well. Of course the biggest risk is the delivery of energy resources, especially gas," he added.

RUSSIA'S 'TROJAN HORSE'

Bulgaria was seen as Russia's most pliable ally in Soviet times and to this day its leaders have to fend off accusations that the country is a "Trojan horse" inside the EU, secretly working in the interests of the Kremlin.

Its Cold War alliance left a deep economic footprint on the Balkan state, especially as it is almost entirely dependent on Russian energy supplies. More than 85 percent of gas is bought from Gazprom, its only oil refinery is controlled by LUKOIL and its only nuclear plant runs on Russian fuel.

Despite joining NATO ten years ago, and taking part in U.S.-led war games since the Crimea crisis erupted, Bulgaria's armed forces are similarly dependent on Russia for repairs and spare parts for their Soviet-made jet fighters and tanks.

Russia is Bulgaria's second biggest trade partner and imposing tough economic sanctions on Moscow would hit about 2,000 Bulgarian companies, employing about 80,000 people, who depend on business with Russia, the foreign minister said.

Russian holidaymakers are the lifeblood of Bulgaria's tourism industry, which contributes about 13 percent of the country's gross domestic product, prompting fears about what would happen if the EU restricted Russians' entry into the bloc.

About 700,000 Russians - a figure equivalent to a tenth of Bulgaria's population - visited the Black Sea state last year. They travelled to resorts such as the coastal town of Pomorie, so full of Russian sunseekers and homeowners that one of its districts is called "Little Moscow".

Worries about the economic damage a prolonged standoff with Russia could cause, coupled with nostalgia for communism among the older generation and a growing disillusionment with the EU, have prompted calls by some for closer ties with Moscow.

"Bulgaria should veto any, I repeat, any sanctions on Russia," said Emil Vangelov, a retired teacher in Sofia. "On the contrary, we should expand our economic, political and cultural relations with Moscow. Can't you see that Bulgaria is disappearing after all the lies from the U.S. and EU?"

SNAP ELECTIONS?

The decorations in the office of Attack party leader Volen Siderov leader offer clues as to why the country's fragile coalition government, which has only just emerged from one political crisis, could soon be heading for another.

Antique swords and pistols hang on the wall, some of them relics of Russia's battles with Turkey in the 19th century, which liberated Bulgaria from 500 years of Ottoman rule. Propped up on the floor lies a painting of the medieval school of Tarnovo, the capital of the Second Bulgarian Kingdom, whose teachings influenced the Russian Orthodox church.

Bulgaria's ties with Russia, with whom it shares a similar language and the Cyrillic alphabet, are stamped on the cityscape of its capital. Sofia's most prominent monument is the Alexander Nevsky Cathedral - built in thanks to the tens of thousands of Russian soldiers who died fighting for Bulgaria's freedom.

Siderov has played on such historical associations to whip up pro-Russian feelings among voters ahead of European elections in May, a vote that is seen as a key test of the Bulgarian government's long term survival.

The Socialists could lose the votes of supporters angered by the government's going along with sanctions. A direct descendent of the Communist regime in power before the fall of the Berlin Wall, the party has a strong pro-Russia wing and much of its older, rural vote base leans more towards Moscow than the West.

The ruling party has been beset by internal squabbles and, even before events in Ukraine began, faced the prospect of losing votes in May to a leftist splinter group led by a former president, and another movement led by a former TV anchor.

As things stand, the right-wing GERB party will likely come out on top in the EU polls, a scenario that could spark a snap general election in the autumn.

Street protests felled one government in Bulgaria last year and almost toppled the current administration, which has survived three confidence votes since taking office. Another bout of instability could further hamper much-needed social and economic reforms in the EU's poorest member. (Additional reporting by Angel Krasimirov; Editing by Giles Elgood)